The 5 Best Under-Sink Water Filters of 2023

Final Verdict

For most users, the Aquasana Claryum 3-Stage Max Flow is our top pick, thanks to its ease of use, fast filtration rate, and innovative multi-filtration technology. However, if you’re lacking the cabinet space and want a more affordable option, the EcoPure Main Faucet Filtration System comes in as a close second, thanks to its unique, space-saving design and DIY installation.

How to Shop for an Under-Sink Water Filter Like a Pro

Type

The type of filter(s) plays an important role in both the price and effectiveness of an under-sink water filtration system. There are generally three different types of filters available on the market, and the one you pick will most likely depend on your budget and the type of filtration you need. Here’s a quick primer on the different types of water filters: 

• Carbon Filter: A carbon filter is the most basic option when it comes to filtration, but still very effective. In this case, activated carbon will chemically bond with contaminants, removing them as water flows through the filter. However, all carbon filters aren’t created equal, so the effectiveness of a carbon filter alone will vary. You should look for the level of filtration noted on the product, including the contaminants it will remove.
• Reverse Osmosis Filter: The most heavy-duty option, reverse osmosis systems flush contaminants from the water supply to deliver filtered water through a separate faucet. The system works by pushing water through a membrane with pores that are incredibly small, so that only water molecules can pass through. That makes reverse osmosis filters the most effective, with the ability to eliminate thousands of toxins such as chlorine, fluoride, and heavy metals, as well as bacteria and pesticides. However, many take up a considerable amount of cabinet space and are pretty difficult to install, which means you’re better off relying on a professional.
• Ultrafiltration: Ultrafiltration uses a hollow fiber membrane to stop debris and contaminants from entering the water. It’s not as effective as a reverse osmosis system, but it can preserve the healthy minerals that are eliminated in systems where only water molecules pass through. These systems are also easier to install, as they generally work as an addition to the existing faucet. However, in these cases, the filters will need to be changed much more often.

Filter Replacement

“Most filters need to be swapped every six months and cleaned periodically,” says Pinchev. “Due to this, I would recommend looking for options where the filters are relatively cheap and easy to purchase, and also allow easy access, so they can be cleaned without tearing the whole system apart.” After all, there’s nothing worse than buying an under-sink water filtration system, only to realize that its preferred filter has been discontinued.

Installation

Most filters come with detailed instructions on how to install them, according to Lewin, and they’re usually easy enough to install on your own. However, if your setup requires you to drill holes in your faucets or valves, Lewin recommends you get professional help—provided budget isn’t an issue.

Questions You Might Ask

What are the benefits of an under-sink water filter?

“There are several benefits of installing an under-sink water filter rather than using a pitcher filter or whole-house water filter,” insists Pinchev. Below are some of his top few:

• They’re more convenient since you don’t need to keep refilling pitchers.
• They don’t take up valuable counter space, especially in small kitchens.
• The filtration is more targeted: It only purifies drinking water and doesn’t waste filtered water on washing dishes or showering.
• It affords better filtration than pitcher options, because under-sink water filters use water pressure (not gravity) to push water through the filter.
• The cartridge doesn’t need to be replaced as often as a pitcher filter might (e.g. six months minimum versus two months).

How do you install an under-sink water filter?

Each system can be different, but overall, there are some general guidelines for installing an under-sink water filter, according to Lewin. “If your sink doesn't already have a spare faucet slot, you'll need to drill one,” he says, reminding you to ensure that your water supply is turned off. “Once everything is prepared, locate your cold water pipe. Unscrew the pipe that connects the faucet to the cold water pipe, and connect the T-valve (usually included in the box) in the middle. Use Teflon tape around the threads on the connections to prevent leaks. Then, connect the plastic pipe and the shutoff valve (both usually in the box) to the T-valve.” 

Next, you’re ready to put together the faucet by following the steps in the manual, which Lewin says is usually the hardest part. Once that’s done, however, all you will have to do is mount the faucet on top of the sink.

How often do you need to change your under-sink water filter?

This will depend on the model you choose, but generally six months is the rule, says Lewin. Many options will also have auto-off functions or other indicators that will inform you when it’s time to change your filters, so you'll never have to worry that you’re using an ineffective one. 

“I usually recommend people ignore the estimated lifespan length and focus on the number of gallons,” adds Lewin. “You can then estimate how often you'll need to change the filter, based on your own family's usage.”

Take Our Word for It

This article was written by Nikhita Mahtani, a freelance writer with six years' experience writing and editing for home publications. To come up with this list, Nikhita researched the best under-sink water filters and consulted Gabe Pinchev, founder and CEO of FieldPulse, an online platform for service contractors, as well as Paul Lewin, a plumbing expert and founder of home maintenance blog Home Water Research.